text:
What are the ICAO RNAV equipment codes for the non-WAAS G1000 and GNS 430W?
When filing an ICAO IFR flight plan, where in "the manual" (which manual?) for a G1000 and a GNS430 do I find the RNAV capability information for an ICAO flight plan? What am I looking for?

Garmin's ICAO Equipment Guide is very helpful indicating

Non-WAAS
G1000                - R and PBN B2, C2, D2
WAAS
GNS 430W             - R, B, and PBN B2, C2, D2

This corresponds with AIM TBL 5-1-6 which can include "up to a maximum of 8 entries"

But where do I find this in the manual?
Garmin also has this ICAO PBN/RNAV-RNP Codes site which explicitly states:

Note: Please reference your navigator and transponder's Aircraft Flight Manual Supplement (AFMS) for details on which codes apply to your avionics.  For integrated flight decks please consult your OEM.

After an Internet search, I found an example Diamond DA40 Airplane Flight Manual Supplement G1000 Integrated Avionics System
I believe the answer is in the SECTION I GENERAL on page 9. This still depends on knowing what exact equipment you have. For example:

Oceanic/Remote per FAA Notice 8110.60 -- Two FMSs are
required to be installed...

Please leave a comment this was helpful to anyone else, or if anything is inaccurate or missing.

Is there a way to make it not a wiki, or do I need to delete and repost? I found I cannot delete and repost (at least not in a near time frame).


text:
When can I start an approach if I lose comms and my clearance limit is not an initial approach fix?
Here is the AIM's definition for a clearance limit:

CLEARANCE LIMIT− The fix, point, or location to which an aircraft is cleared when issued an air traffic clearance

Assume a clearance such as:
"Cleared to Los Angeles Internal Airport (KLAX) via..."
This means our clearance limit is KLAX.
But what does this mean if I follow the instructions in 91.185?

If the clearance limit is not a fix from which an approach begins
[it's not], leave the clearance limit at the expect-further-clearance
time if one has been received [it hasn't], or if none has been
received, upon arrival over the clearance limit

A pilot should fly until the last fix on the route and then direct to their clearance limit: KLAX at their last assigned altitude (let's assume FL280).

and proceed to a fix from which an approach begins

Now fly direct from KLAX, with no assigned route, to an Initial Approach Fix (CRCUS or SEAVU).

commence descent or descent and approach as close as possible to the
estimated time of arrival as calculated from the filed or amended
(with ATC) estimated time en route

Hold at SEAVU or CRCUS (for which there is no published hold--so they can make one up), UNTIL their ETA into LAX. Then, descend in the hold and fly the approach. Or, realizing these fixes are 35nm away from KLAX, would a pilot turn around half way between SEAVU and KLAX to return to SEAVU at their ETA to descend?
Is that crazy to anyone else? To follow this regulation, a pilot would fly over their destination airport and then return to an IAF to do an approach. Does ATC really want us to do this in a lost comm situation? At a minimum, this doesn't seem like a prudent use of fuel which brings safety of flight into the mix.
When and where can I legally start an approach in this scenario?

I edited your question a bit to (hopefully!) make it more specific and less likely to generate discussion; that's how this site is intended to work best. If I changed it too much then of course feel free to roll back or edit again. BTW, please use the quote formatting for quotes to help screen readers and other software work better.

I like it. Good work!

Note: this may be a dupe of this question. However, you seem to be saying that you've read and understood the regulations on what to do, you just don't believe that ATC or the FAA really expects you to follow them.

In the scenario you describe you are indeed expected to fly from the airport to an IAF before beginning an approach. There's a long and detailed article in IFR Magazine about clearance limits, which discusses the regulations and the practical options. It makes a similar point to yours about lost comms:

Since the clearance limit is the
destination airport, very few approaches start there. An airport is
never used as a fix in IFR. A fix is an intersection, waypoint or
NAVAID. Moreover, receiving an EFC time in advance is simply silly.
This would also presume the issuance of holding instructions. Why
would a controller issue these things since lost communication cannot
be predicted?

It also acknowledges that many pilots share your opinion on the lost comms action:

Many pilots disdain these rules as onerous, unnecessarily
time-consuming and complex.

The article then notes that there have been multiple attempts to change the FAA's mind:

Since 2009, there have been about five challenges to this rule. In the
latest iteration, our past editor, Jeff Van West, wrote the Office of
Chief Counsel in late 2017, arguing that 91.185 (c)(3)(ii) is
inconsistent with current air traffic practices and creates an
unnecessary hazard.

But, you can read that 2017 legal interpretation yourself and you'll see that the FAA really does expect pilots to follow the regulation as written:

As you correctly state in your letter, the requirements of §
91.185(c)(3)(ii) are rarely in effect thanks to the improved technology ensuring that communications between pilot and ATC are not
lost. However, the requirements of (c)(3)(ii) are necessary to ensure
the safety of the NAS when a pilot is unable to communicate with ATC.
[...]
we affirm our previous interpretations of § 91.185(c)(3).

So that's the official answer for now (unless I missed a more recent interpretation).
Finally, if you want an alternative course of action, IFR Magazine's suggestion is to fly from the airport to an IAF and then invoke emergency authority to start a descent immediately, without holding:

ATC does not want you flying a holding pattern while it’s diverting
traffic everywhere to avoid a conflict. You have unintentionally shut
the airport down. When you reach an IAF of your choosing, ATC will
know which approach you intend to use. At the IAF, use your emergency
authority and begin descent.

That complies with the regulation and although it burns more fuel your priority should be acting predictably and landing safely. An IFR reserve should be plenty to allow for the extra flying time: KLAX to SEAVU is about 45NM, which isn't much time at jet speeds.

I had read an article on this years ago; but I've been scouring the Internet, and I couldn't find it. Thank you for the great response! I looked at the answer you referenced, and it seemed to gloss over these finer-point-details which you eloquently covered.

The main takeaway is that ATC with a comms failure will expect you to take the most logical and sensible path and take action (clearing traffic) based on that expectation.

I will concur and say what "the FAA" expects a pilot to do and what "the controller" expects or desires a pilot to do may not always line up.

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sort: votes


text:
Where are aeroplanes sent to if they are not be used for periods more than 3 years?
We were looking at the type of facilities and the sort of suitable environments/and or conditions for aircraft storage and a part from "indoor" it was mentioned that places that are humid is also ideal. Is there are location out there in the world that meets such criteria and/or a place that aeroplanes are sent to "rest" during this period and is there are term for such a place.

Who told you humid was good?  That's a recipe for mold.  Dry climates are best, there is a reason the US military uses Arizona.

@MichaelHall Yep, humidity is the enemy. Perhaps you meant humidity controlled, Ludwif?

The opposite of "humid" is why the aircraft boneyard for the USAF, US Navy, and multiple airline companies is in the Arizona desert.

My apologies and thank you for the correction. But realistically the conditions we experience at either side of the world  is not that totally dry all. If it were you and I wouldn't be breathing this air. Air needs to have some level of moisture in order for it to become breathable. However, I'll consider dry as 'there is little or less amount of absolute humidity in the air'.

Humidity and cold are optimal conditions for cigars

"Air needs to have some level of moisture in order for it to become breathable": I don't believe this.

To add just a little to WPNSGuy's correct answer:
In addition to year-round near-zero humidity and minimal rain and snow, you also need no salt in the environment, cheap real estate, and ready access to a big airport. Several places in Arizona check all these boxes.
Note that because of the intense sunlight with lots of UV in it, you have to protect things like de-icing boots, plastic antenna housings and plexiglass windows by taping them over with protective film- which also protects them from sandstorm damage.
To keep little critters out of the engines and airframe, you also have to plug things like oil cooler inlet scoops and the intake and exhaust ducts of the engines and APU's.
The whole process is a well-developed business called mothballing. A change in fuel costs of just a few percent over time is sufficient to send whole fleets of particular aircraft into mothballs, only to return to service when those costs drop again.
When teaching materials science, a standard exercise is to ask the students why aluminum aircraft that are crashed on tropical rain forest islands in the Pacific literally "melt" into the jungle within years while an identical airplane parked in the Arizona desert shows no ill effects for decades. The answer is that salt plus humidity plus rain plus warm temperatures means rapid corrosion of aluminum alloys. Remove the salt and water, and the corrosion rate of the aluminum drops to very very low levels.

PS- it is not true that humans need some humidity for air to be breathable. It is perfectly breathable regardless of ambient humidity because your nasal passages humidify it for you exactly as required.

These information has explained a lot. Mothballing is a new term for me. I reckon the cause of this aluminiummelting is due to salt and acid rain. Thanks a lot

Where?
In the USA, Arizona.
There are several facilities in the Arizona desert for this function.
https://www.airplaneboneyards.com/arizona-airplane-boneyards-storage.htm
ex: Pinal Airpark, in Marana Arizona.

It acts as a "boneyard" for civilian commercial aircraft as well as a
site for airliner storage and reconfiguration.
Out-of-service aircraft are stored there as the dry desert climate
prevents any form of corrosion.

Don't forget Mojave, California, another favorite.

Central Washington also sees some use.  Grant County International isn't quite as dry as Arizona, but it's more convenient, particularly for aircraft that probably only need short-term storage.

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text:
What happens if the current ICAO method disagrees with double wheel/dual tandem etc?
Is the old U.S. method (a weight max for each landing gear kind) simply ignored? Planes with 3, 12, 14 and 22 wheels are common after all but gear types with those numbers often aren't listed. If the old way's ignored for 6, 10 and 18 wheels too then why's it often shown with the (soon-to-be replaced by ACR-
PCR) ACN-PCN method? For example JFK has Pavement Classification Numbers from 90RBWT to 148FAWT (!) but the runways are all 210,000/550,000/1,000,000 lbs despite that vast strength difference (if a plane taxis from F to R and/or A to B its Aircraft Classification Number even gets worse). Another oddity is the 787-9 has 550,000-type tandems so old way would say it's too heavy till 11,500 lbs under MTOW but ACN-PCN says JFK runways are proof for fully-loaded 789s (90RBWT is obviously overkill for the relevant ACN of 71 and 60 on the 148FAWT runway is very overkill strengthwise (lengthwise it's OK for many landings but 1000' under nominal takeoff))

Welcome to aviation.stackexchange.com. This question could be improved by adding a bit more context. I understand it is about differences between ICAO and FAA regulations, and it has to do with wheels , weight and pavement classification, but that's about it. If you would quote the ICAO text and the (old) FAA text, and then explain what the inconsistency is, there is a much higher chance of getting good answers. Now you leave it up the readers to go throught the ICAO SARPS (several thousand pages) and the (old) FAA regulations (similar volume) and they have to guess what you are referring to.

It's about ICAO ACR-PCR system introduced by amendment 15 to Annex 14... (see next comment, due to url length)

... related FAA AC are 150-5335-5D, and 150/5320-6G. In the first document, FAA says: "An updated ADM Part 3 with the new procedures will
be posted in the near future"

Sorry about that. I added context.


text:
What is the best glide speed for the DC-3 with 2 engines out?
What is the best glide speed for the DC-3 with 2 engines out?
I realize we may consider best speed for ground distance traveled or best for duration - and that weight can be a factor. I can't find anything on the web.

Maximum glide angle for the DC-3 with power off, both propellers feathered, gear and flaps up, no wind is computed to be 3.88 degrees. This angle will give the maximum glide range. Depending on the aircraft's weight the following numbers can be applied to give the maximum distance:
20,000 lbs. Gross Wt. IAS 92K   (MPH 106),
23,000 lbs. Gross Wt. IAS 99K   (MPH 114),
26,000 lbs. Gross Wt. IAS 104   (MPH 120),
The rate of sink at 20,000 lbs gross weight is approximately 680 feet per minute (11.3 ft per sec.) at 5,000 ft of altitude.


text:
What is this fighter jet that flew over KJST?
This aircraft was doing low level flights over my office a few minutes ago.  From the route it was flying some of my coworkers thought it might have been doing approaches or touch and go landings at the local airport (Johnstown, PA (KJST)).

After it left the area I tried comparing it against pictures of active US fighters; but the wings didn't appear to match with anything I saw.

What local airport? Could help to identify by knowing what air wings are stationed nearby. It looks like the YF-17 but only two were made and it never saw production after the initial 2 in 1974. Both aircraft are supposedly on display, one in Torrance California and one in Mobile Alabama. It is probably an F-18 variant though, the wings look a little different but it could just be perspective.

The fusilage's single curve does seem to fit the YF-17 better than an F-18.  I can't imagine what one would be doing around here though even if it was flying though.

It's an F/A-18 Super Hornet.
Defining characteristics:

Slightly angled twin vertical tail
Twin engine with little space between them (eliminating the F-14 and similar)
Almost straight trailing edge of the wings
Horizontal tail with significant sweep angle that also protrudes behind the engine exhaust
Massive wing strakes (thanks Dan Pichelman!) along the fuselage under the cockpit
The wing "notch", as noted by Ron Beyer in the comments

Also the shape of the horizontal tail excludes the YF-17:

Source
As mentioned by Penguin, the wing notch, together with the single curve leading edge extensions are the indicators that mark this aircraft as a "Super" variant (E-F, single seat and two-seat, respectively) rather than an earlier vanilla "Hornet" variant (A-C), as seen in this figure:

Source
Note also the less round profile of the horizontal tail, like the one seen in OP's photo.

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text:
What are the reasons for using hydraulic power on major aircraft systems?
What are the actual benefits or advantages of using Hydraulic energy in aircraft systems, compared to pneumatic and electrical systems.

It's very compact.

This is a broad question, I'm sure whole books could be written on this subject.

Just imagine using an electric motor on an excavator. It's possible, but more complex. Hydraulic is powerful, we just need a small jack to move a huge mass.

Hydraulics don't compress so more positive displacement. Hydraulics run at high pressure so smaller actuators can be used. Hydraulic leaks are visible. Pneumatic leaks aren't.

A comparison with electric motors/actuators can be seen in this thread: Why do most commercial airplanes use hydraulics instead of electric/servo motors?

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text:
What would be the feasibility of an auto-rotating landing gear system?
Has a feasibility study been considered that would allow for auto-rotation of heavy commercial aircraft landing wheels so that tire rotation matches air speed pre-landing?


text:
Can two Airlines have the same ICAO code but different IATA codes or vice versa?
We are trying to import all the Airlines into a Table.
Plan is to Update existing Airline Data if not present then create it.
For this we needed an unique way to identify the Airlines.
Is ICAO+IATA an unique identifier or is it possible to have Airline without IATA or ICAO code?

Can you say where you are getting the list of airlines from for curiosity? Airlines are founded and disappear on an almost weekly basis, so I would be interested in any datasources listing them.

IATA codes are not unique. There simply aren't enough of them and they are expensive to maintain. Additionally the concept of an airline is a little fluid.
The simplest issue to deal with are controlled duplicates, where 2 airlines that are geographically seperated share an IATA.
Another key issue is where an airline may have one commercial brand but several corporate entities each with there own IATA for cabotage purposes. LATAM group is a key example of this, but several european airlines (easyjet and ryanair) are also going down this route to be prepared for brexit.
Many small regional airlines in places like Alaska,the Australian outback and the Caribbean will simply not be able to afford an IATA code, or may make up there own 2 letter code that is not an IATA code.
Finally you have franchise operators like flexflight, who operate a single route themselves to maintain membership, and then provide ticketing services to other small airlines, using there code to interact with the GDSes. In this case, one IATA code can represent many potentially geographically overlapping airlines, but they are usually separated by something, often flight number.
If you wish to track all airlines in general, you are going to have to come up with your own id.


text:
Is there a generic term for origin and destination seen from an airport point of view?
I am trying to create a program that gives you the departures or the arrivals from a given airport.
Thus, in the software code, I would like to refer to both origin anddestination with the same term, in order to print the former if the user requested arrivals, and the latter if the user requested departures.
So basically I want to know if there is a common name for these two terms, when speaking from the airport point of view, i.e. referring to a generic flight, regardless of it being inbound or outbound, what is "the other airport" in the jargon?

Do you want to use this term when displaying the output, or just for the code?

Why not just use "airport", it's already a generic term that could be an origin or a destination.

@Geoff No doubt "airport" will already be used to refer to the base airport being searched. This might be a question better suited to Stack Overflow; nevertheless I'll throw in my two cents and suggest a simple solution being HomeAirport and AwayAirport. I don't think there's a universal term so I doubt you'll get a concrete answer.

On English.SE: Word for an Origin and Destination without regard for route

Thanks for the link foot, and regarding your question, I just need it for the code, so the end user won't see it.

Perhaps the “remote” airport — that should work for both arrivals and departures.

Thanks for the quick answer, I really like remote as an option

What you are describing is a way to sort and select flights, consisting of a departing airport and an arriving airport. An airport is a node in the directed graph of flights, and its meaning is predicated on whether you are looking for arrivals or departures.
Departing           Flight                    Arriving
Airport[1]----------Flight[1]---------------->Airport[2]

If you are looking for a word to call the airport you aren't at (local) I could see "remote" or "external"

Thanks for the detailed answer. I get what you mean. I was just trying to find a single comprehensible word to refactor the code, but maybe it just doesn't make sense.

For code refactoring you would get more answers over on StackOverflow or Software engineering.SE.

The "connection" airport maybe? Could refer to where a plane is coming from, or where it's going to.

Maybe I'm wrong but connection to me suggests a stopover in a flight with stops. Thanks for the answer!

In statistical reports, departures+ arrivals= movements

I understand that, however I understand movement more as a flight rather than as an airport. Thanks for the quick answer!


text:
Why would there be flight restrictions when the barometric pressure exceeds 31 inHg?
FAR 91.144 states that flight restrictions may be issued by notam when barometric pressure exceeds 31" Hg.  Why would such a restriction be necessary?

I presume this is an issue with safety of flight, but I don't understand what unsafe condition might occur.  It seems to me that an abnormally low barometric pressure might be more of a problem, but perhaps that is skipped because the thread of adverse weather is more obvious, and dealt with elsewhere in the regulations.

It is because standard altimeters are not adjustable beyond this range. The AIM 7-2-2 contains information on how to handle it:

When the barometric pressure exceeds 31.00 inches Hg. The following procedures will be placed in effect by NOTAM defining the geographic area affected:

(a) For all aircraft. Set 31.00 inches for en route operations below 18,000 feet MSL. Maintain this setting until beyond the affected area or until reaching final approach segment. At the beginning of the final approach segment, the current altimeter setting will be set, if possible. If not possible, 31.00 inches will remain set throughout the approach. Aircraft on departure or missed approach will set 31.00 inches prior to reaching any mandatory/crossing altitude or 1,500 feet AGL, whichever is lower. (Air traffic control will issue actual altimeter settings and advise pilots to set 31.00 inches in their altimeters for en route operations below 18,000 feet MSL in affected areas.)
(b) During preflight, barometric altimeters shall be checked for normal operation to the extent possible.
(c) For aircraft with the capability of setting the current altimeter setting and operating into airports with the capability of measuring the current altimeter setting, no additional restrictions apply.
(d) For aircraft operating VFR, there are no additional restrictions, however, extra diligence in flight planning and in operating in these conditions is essential.
(e) Airports unable to accurately measure barometric pressures above 31.00 inches of Hg. will report the barometric pressure as "missing" or "in excess of 31.00 inches of Hg." Flight operations to and from those airports are restricted to VFR weather conditions.
(f) For aircraft operating IFR and unable to set the current altimeter setting, the following restrictions apply:
   (1) To determine the suitability of departure alternate airports, destination airports, and destination alternate airports, increase ceiling requirements by 100 feet and visibility requirements by 1/4 statute mile for each 1/10 of an inch of Hg., or any portion thereof, over 31.00 inches. These adjusted values are then applied in accordance with the requirements of the applicable operating regulations and operations specifications.
EXAMPLE-
  Destination altimeter is 31.28 inches, ILS DH 250 feet (200-1/2). When flight planning, add 300-3/4 to the weather requirements which would become 500-11/4.
   (2) On approach, 31.00 inches will remain set. Decision height (DH) or minimum descent altitude shall be deemed to have been reached when the published altitude is displayed on the altimeter.
NOTE-
  Although visibility is normally the limiting factor on an approach, pilots should be aware that when reaching DH the aircraft will be higher than indicated. Using the example above the aircraft would be approximately 300 feet higher.
   (3) These restrictions do not apply to authorized Category II and III ILS operations nor do they apply to certificate holders using approved QFE altimetry systems.
(g) The FAA Regional Flight Standards Division Manager of the affected area is authorized to approve temporary waivers to permit emergency resupply or emergency medical service operation.
b. At or above 18,000 feet MSL. To 29.92 inches of mercury (standard setting). The lowest usable flight level is determined by the atmospheric pressure in the area of operation as shown in TBL 7-2-1.

So because most altimeters do not have this kind of range, the altitude readout will be inaccurate. This is especially problematic for IFR operations where you do not have visual reference to the ground.

I think I found the answer.  The Standard governing manufacture of sensitive altimeters is TSO-C10b.  TSO-C10b cites SAE Aeronautical Standard AS 392C.  This standard specifies two types of altimeters:

Those with a range to 35,000 feet.
Those with a range to 50,000 feet.

Both are required to be adjustable for barometric pressures between 28.1 and 30.99 inches of mercury.  FAR 19.144 specifies an atmospheric condition which exceeds the specifications required for altimeters.


text:
What are the specific number of passengers and conditions required to select HI, NORM, or LOW on the pack flow knob?
On the Airbus A320 there is a pack flow knob and you can either select HI(120%), NORM (100%), or LO (80%). You choose which one according to the number of passengers and ambient conditions. Obviously If you have a full flight and it is hot outside you would choose HI. Or if you have very little passengers and it is cold or even raining outside you would select LO. But is there a specific number of passengers when you would select HI or LO, or is there a specific temperature, or both?

From the A320 flight crew operating manual (FCOM):

The selector is kept to NORM in most conditions.
It can be turned to LO:

When the number of passengers is low. 115 passengers is indicative and there are local regulations about the quantity of air which must be delivered per passenger. Operators may have different instructions in their SOP.
When fuel is low for some reason. Using more bleed air increases fuel consumption.
It is also tempting for an operator to reduce fuel and maintenance costs by also reducing air flow. See this thread on PPRuNE.

Air flow can be increased to HI:
Automatically:

When the other pack is turned off.
When APU provides bleed air.

Manually:

When air is too wet due to perspiration and breathing. Dampness increases with the number of passengers.
Air in the aircraft contains smoke.
To intentionally increase tapping of bleed air from the engines, which increases compressor stall margin. This would be desirable while flying in a volcanic ash cloud.

Packs also provide air for pressurization purpose (PACK stands for pressurization and air-conditioning kit). In case of leakage, air flow can be increased. In emergency situations, bleed air can be replaced by ram air (ram air is normally only used for cooling bleed air, but doesn't enter into the pressurized sections of the aircraft).

So there is no specific temperature for HI


text:
(Ref AC 61-65H solo endorsements 61.87(n) and 61.87(p)). When should I give 61.87(n) vs 61.87(p)?
At first, it seems clear (according to AC 61-65H) that 61.87(n) is for the first 90 calendar-day period and 61.87(p) is for each additional 90 calendar-day period. However, when I look up the actual regs, it says: "(n) Limitations on student pilots..." and "(p) Limitations on flight instructors..."
So, now it seems like (n) should be the only 90 day endorsement. (p) are just the rules the flight instructor has to follow (every time). So don't (n) and (p) always go together? And, is this idea that we start with (n) and then use (p) if 90 days go by...incorrect? Dare I say, should there be an AC 61-65I that corrects this? And, what should the endorsement say?
I see the NAFI guide sets up the question the same way the FAA does (initial vs additional 90 days), but they just use (n) for both of them.

Remember the ACs are guides, not laws, as opposed to the FARs.
14 CFR §61.87(n) reads:

Limitations on student pilots operating an aircraft in solo flight. A student pilot may not operate an aircraft in solo flight unless that student pilot has received an endorsement in the student’s logbook for the specific make and model aircraft to be flown by an authorized instructor who gave the training within the 90 days preceding the date of the flight.

14 CFR §61.87(p) reads:

Limitations on flight instructors authorizing solo flight. No instructor may authorize a student pilot to perform a solo flight unless that instructor has—
(1) Given that student pilot training in the make and model of aircraft or a similar make and model of aircraft in which the solo flight is to be flown;
(2) Determined the student pilot is proficient in the maneuvers and procedures prescribed in this section;
(3) Determined the student pilot is proficient in the make and model of aircraft to be flown; and
(4) Endorsed the student pilot’s logbook for the specific make and model aircraft to be flown, and that endorsement remains current for solo flight privileges, provided an authorized instructor updates the student’s logbook every 90 days thereafter.

The upshot of which is that (n) is, technically the only requirement for the student to possess for initial authorization for solo flight by a student pilot. (p) is also applicable to the endorsement that must be met by the instructor for initial endorsement, but must be met for additional 90 day solo endorsements by the student.
Here’s the thing, as there is no legal requirement for exactly HOW TO PHRASE an endorsement; they can technically be written by a CFI, provided said endorsement conforms with §61.87, you’re perfectly welcome, as a flight instructor, to give an initial endorsement referencing both (n) and (p) if you desire.


text:
What are the required CFI-A Initial Endorsements?
What endorsements are required to be given for a CFI initial checkride? (It seems unclear what the exact answer is and ultimately up to the DPE)
First of all, 61-65H contains 2 endorsements which do not seem to be required:
A.41 Fundamentals of instructing knowledge test: § 61.183(d).
A.42 Flight instructor aeronautical knowledge test: § 61.183(f).
per the FAA Airmen Knowledge Testing Matrix The Flight Instructor Airplane and Fundamentals of Instruction, "Requires NO instructor endorsement or other form of written authorization"
AC 61-65H lists roughly 4 to 6 endorsements required for initial CFI:
A.1 61.39(a)(6)(i) and (ii) Training time in 2 calendar months previous
A.2 61.39(a)(6)(iii) Knowledge Test Deficiencies
A.41 Fundamentals of instructing knowledge test: § 61.183(d). see above testing matrix contradiction
A.42 Flight instructor aeronautical knowledge test: § 61.183(f). see above testing matrix contradiction
A.43 Flight instructor ground and flight proficiency/practical test: § 61.183(g). This references required training of § 61.187(b).
A.45 Spin training: § 61.183(i)(1).
The DPE I spoke with said he also wanted to see a statement or endorsement of the 4 items listed in the PTS under Flight Instructor Responsibility. He said the A.41 endorsement above was required, but not the A.42 based on the FAR. I read the FAR, and I think it's already covered by 61.187(b).
The FAA has a document which lists Initial Flight Instructor Endorsements five endorsements which includes a self endorsement. The CFI Academy seems to agree with the FAA's list, however there's a great comment which points out that 61.195(i) that “A flight instructor shall not make any self-endorsement...
In summary, what do you guys say? What endorsements are required for CFIA initial?

Definitely no self-endorsing. I'm confused why the DPE wants to see the endorsement for the FOI KT, A.41. I showed up to my CFI ride with A.1, A.2, A.43, and .45 and the examiner was happy.

I also showed up to my CFI-A practical with only those mentioned by PilotDan many years ago.  Every year CFI's self endorse they accomplished the required TSA training.  So the self-endorsement ban is for pilot related duties and not instructional duties.

Short answer: as far as I can see, the six endorsements listed in AC 61-65 are the required ones: A.1, A.2, A.41, A.42, A.43, A.45.

That's based on the FAA's own internal instructions on how to administer a CFI initial checkride, which say (section 5-500C):

C.    Record/Logbook Endorsement. An ASI, establishing the eligibility of an applicant for a flight instructor certificate, must
determine that the applicant meets all applicable requirements of part
61 subpart H. Applicants for an initial flight instructor certificate
must satisfy the aeronautical knowledge requirements of § 61.185, as
discussed in subparagraph 5-500A. To document eligibility, applicants
must possess and present a record of aeronautical experience and a
training record certified by the authorized instructor who provided
the training for the flight instructor certificate sought. Records
include logbook entries of training received and endorsements similar
to the sample endorsements provided in Advisory Circular (AC) 61-65,
Certification: Pilots and Flight and Ground Instructors.
NOTE:  AC 61-65 provides a complete list of example endorsements
required for a flight instructor practical test (initial certificate
or additional rating).

Per 61-65H, A.41-A.46, that list for CFI-A would be:

A.41: Fundamentals of instructing knowledge test: § 61.183(d)
A.42: Flight instructor aeronautical knowledge test: § 61.183(f)
A.43: Flight instructor ground and flight proficiency/practical test: § 61.183(g)
A.45: Spin training: § 61.183(i)(1)

It also says under A.43 that "The endorsement for a practical test is required in addition to the §61.39 endorsements provided in endorsements 1 and 2 (see paragraphs A.1 and A.2)." So that's two more endorsements, for a total of six.
As to your other points:

The testing matrix lists the requirements for the written (knowledge) tests, not for the checkride. You don't need the endorsements to take the written tests, but you do need them for the checkride.
But, the wording of the knowledge test endorsements is definitely strange, as you noted. 61.183(d) says the requirement is to "Receive a logbook endorsement from an authorized instructor on the fundamentals of instructing listed in §61.185 of this part appropriate to the required knowledge test". There's nothing there that requires the endorsement before the test1, but the AC 61-65 wording is "I have determined that [he or she] is prepared for the Fundamentals of Instructing knowledge test." I don't know why the AC has that wording but I'd guess it's sloppy editing. Perhaps the endorsement was required in the past but isn't today, or perhaps it was a copy/paste thing from other, similar sections.
There's no explicit requirement to have an endorsement for the four ACS items you mentioned, and I don't know why the DPE asked for them. It's true that the ACS says "The flight instructor must certify that the applicant is [...]", however all four items are already covered by other endorsements, at least as far as I can see. Sometimes it's just easier to give the DPE what they want, of course, but I'd ask (or ask your instructor to ask) them for more details on why the other endorsements don't cover the ACS points.

1 Compare that with 61.103(d)(2) for private pilots, which does say the endorsement comes first: "[...] the person is prepared for the required knowledge test"

Thank you for the short answer :-) . The two knowledge test endorsements bug me. In the FAR, 61.183(f) Flight instructor aeronautical knowledge test only needs to be passed but not endorsed, and that agrees with the testing matrix. However, FAR 61.183(d) references "endorsed...appropriate to the required knowledge test." It seems they mean "practical test." The wording doesn't make sense. Why require an endorsement for a knowledge test--which is not required for the knowledge test--but is required for the practical test? Maybe I should write the FAA :-/

@JavaAddict Thanks, and I agree about the strange wording!


text:
How to determine if flow transitions or separates from a Cp plot?
I came across this image:

My question is: given a general Cp plot, how does one tell from the shape of the curve if flow transitions or separates? Specifically, what features on the plot do I look out for that can tell me if flow transitions or separates (e.g. inflection points, plateaus, etc)
I know that a strong adverse pressure gradient causes separation which shows as a steep downward slope on the graph. What I don't know is where exactly on the graph transition or separation happens.

Separation happens at the separation point, when the steep pressure gradient suddenly changes to a plateau, and transition happens at the transition point when the plateau changes back to a steep pressure gradient. Reattachment is a little harder to discern: Here the slope of the pressure gradient, which is quite steep right past the transition point, changes back to something close to its inviscid value.
It helps to plot the inviscid pressure distribution (dashed lines) together with the "real", viscous one (solid lines), as shown below for an Eppler 502 at 3° angle of attack:

The blue line shows the pressure coefficient on the upper side and the red one on the lower side. On both sides there are laminar separation bubbles, but the one on the bottom is much bigger, so I will focus on this one. In a way, the plot lines, or more precisely the difference between inviscid and viscous pressures, mirror the behaviour of the boundary layer: With the separation the boundary layer thickens as the outer flow lines move away from the wing contour. With the transition the flow lines bend towards the contour again and at the reattachment they continue to follow the contour.

Detail view of the plot above.


text:
How to calculate the amount of thrust of a autogyro during auto rotation?
When a autogyro/gyrocopter is in a horizontal steady flight the rotor should be able to provide enough thrust using the auto rotation principle if the horizontal speed can be regulated by the vertical propeller.
I was wondering how the amount of thrust provided by the main rotor of a autogyro during auto rotation can be calculated. All the characteristics of the autogyro and his blades are known.
The horizontal speed of the gyrocopter can be regulated by additional engines and they do not need a specification.

In auto-rotation, either flying level, or with a constant sink speed, the vertical component of the thrust provided by the rotor is exactly the same as the weight of the gyro...
In Wikipedia  https://en.wikipedia.org/wiki/Disk_loading#Momentum_theory  you can find the derivation of the following expression:
$T = 2v^2· A·  rho$
where T is the thrust of the rotor, v the sink speed in vertical auto-rotation, A the 'disk area' (that swept by the blades) and rho the air density.

Thanks for you answer!
I understand that the in steady horizontal flight the thrust is equal to the weight but how can it be calculated. For the formula that you provided a sink speed is necessary, but in this case the sink speed is zero. At least as you specify it as the speed at which the plane is moving down.
That is the part I'm struggling with as I can't seem to understand how this v can be obtained for an auto-gyro in auto rotation at a steady horizontal flight.

It's always he vertical component of the thrust... It's an important detail, because the disk is more or less tilted backwards, except when the gyro is descending in vertical autorotation.   Concerning your doubt regarding v, just imagine the case of vertical autorotation, calculate T for it and use it, correcting for disk tilt, for the case of s/l flight. Now, you don't know the disk tilt, but for high horizontal gyro speeds, that tilt is almost irrelevant...

What do you mean by s/l flight? And if I understand you correct v for horizontal flight is almost equal to v in vertical flight (correcting for the tilt)? There is no possibility to calculate v using the speed at which the gyro is flying and how much the disk is tilted? I'm most interested in a relation between the horizontal speed and the amount of thrust.

By s/l I mean straight and level. The thrust required from the rotor is larger at smaller speeds, because the tilt is higher. I don't know now where to find the value of that tilt as a function of speed, weight, etc. but somewhere in the internet I'm sure you can find it... Ask in the Rotary Wing Forum, for example...

The rotor of an Autogyro does NOT provide Thrust, it provides Drag. This is what differentiates Autogyros from Helicopters, and is why an Autogyro needs a separate engine-driven propeller. So the question needs clarifying as to what you actually want.

Both helicopters and autogyros are kept airborne by the upward thrust generated by their rotors. In the helicopter, the rotor is directly driven by the engine, and its plane can be tilted forward, so that the aircraft may also move forward...   In the autogyro, the rotor is indirectly driven by the engine, via a pneumatic/autorotation transmission, and in forward course, the disk is more or less tilted backwards, the horizontal motion being achieved by the thrust of the prop.

@xxavier the upward thrust generated by their rotors I think the phrase "upward thrust" is confusing. In fixed wing thrust is considered a horizontal component in level flight. Is the term used differently with rotorcraft?

@TomMcW I don't think it's confusing. Rotors and propellers are essentially the same thing, and they both provide thrust...

@xxavier I would say a propeller provides thrust whereas a rotor primarily provides lift. Propellers are using the same principle as wings, but we don't usually refer to it as "lift" because of the direction. I understand what the op is asking, but when I first read the question I thought the same thing: the rotor doesn't provide thrust at all, only lift and drag

@TomMcW All right, you would say it that way, so let it be...

@TomMcW The definitions are indeed pretty straightforward: lift is a force perpendicular to the free air stream, and drag/thrust is a force in line with the free air stream. A fixed wing aircraft has the fuselage + wing all in an arrangement that allows for an easy to understand reference frame. This is not the case in rotorcraft: one could use the same definitions relative to the fuselage, but it is the rotor blades that generate lift & drag, and the free stream relative to the fuselage is now a corkscrew-like twirl. It still makes sense to refer to lift/drag for the blades...

...but for the whole helicopter it is not so straightforward. Yes the rotor produces thrust, which can be pointed at different angles relative to the fuselage, in doing so providing a lifting force and a driving/braking force. The strict separation of definitions that can be made for a fixed wing  cannot be maintained for the rotorcraft. The force provided by an accelerated air stream can always be referred to as Thrust, it is just that the fixed wing guys are lucky that their thrust is always pointing in the same direction: forward.

@Koyovis Dead horse beating: that works for a helicopter, but the unpowered rotor on an autogyro cannot produce any force in the direction of the free steam. It functions exactly in the same way as a fixed wing. Propeller provides thrust, rotor provides lift/drag. But it's really just semantics. I think I was getting on xxavier's nerves. I have a fifth-degree black belt in hair-splitting. I just can't help myself. :P

@RAC rotors and propellers DO provide thrust.


text:
Is more cargo loaded if there is less passengers than expected?
When pre-flight weigh in is done, if the plane weighs less than expected because people don't turn up, is more cargo added?
Conversely - if the plane is over the estimated weight - does cargo get removed?  Passenger bags removed?  Passengers removed?
Is it within the airline's strategy to achieve 100% seat capacity utilisation?

There's what should happen, and there is what can happen if/when people in charge for one reason or another don't care (and the consequences this can have). See e.g. PBS Frontline broadcasted 2010-02-09, titled Flying Cheap at about 43 minutes into the video.

You pose several scenarios.

Is more cargo added if people do not show up?

No. By the time a person does not show up, the cargo is usually already delivered and loaded on the aircraft.

If the plane is over the estimated weight - does cargo get removed? Passenger bags removed? Passengers removed?

Yes, although passengers almost always have priority. On heavy cargo flights, the cargo department will send a priority list if the load planners need to bump cargo.

Is it within the airline's strategy to achieve 100% seat capacity utilisation?

Absolutely, although on payload restricted flights, non-revenue passengers may not always priority over cargo. This depends on the route. Many long-haul flights, if payload restricted, a scenario could happen where a staff member traveling as a non-revenue passenger will not be accepted because accepting them would exceed the max payload for the flight.

While non-revenue passengers do not always have priority over cargo, most of them have priority over everything. Because most of these are crews that will man another flight from where they are heading, mechanics that are needed to fix a broken plane there and such and will incur huge loss if not transported.


text:
How to calculate the velocity gradient at the wall normal to the wall (Boundary layers)?
This problem is from "Fundamentals of aerodynamics" by John D. Anderson, Jr (Fifth edition, page 101):
Consider a flat plate at zero angle of attack in a hypersonic flow at Mach
10 at standard sea level conditions. At a point 0.5 m downstream from the
leading edge, the local shear stress at the wall is 282 N/m^2. The gas
temperature at the wall is equal to standard sea level temperature. At this
point, calculate the velocity gradient at the wall normal to the wall.
I already know: $\tau_w = \mu\left(\frac{dV}{dy}\right)_{y=0} = 282$
but how to get $\mu$ ??
Also I don’t know what this is for: “The gas temperature at the wall is equal to standard sea level temperature”

In page 72 you'll find the value of µ at standard sea-level temperature...

oh I got it, thanks


text:
What are the differences between the proportional flow control FCU and pressure control FCU?
what are the basic differences between the proportional flow control FCU and pressure control FCU? ( FCU : fuel control unit )

See this vs this.

The pressure control system is a typical system as fitted to a turbo-propeller engine where the rate of engine acceleration is restricted by a propeller speed controller
The proportional flow control is a typical system where H.P. compressor shaft r.p.m. is governed by a hydro-mechanical governor which uses hydraulic pressure proportional to engine speed as its controlling parameter
Therefore the pressure control system is one step ahead as it looks at the tendance of speed, of course the pressure control system alone is not sufficient because even if the rate of speed increase is not excessive, the final speed could become excessive, that’s why also a speed limiter is included in the system
Today’s FADECs directly protect the engines for excessive speed and for excessive speed rate
Please refer to to the following Website
http://aeromodelbasic.blogspot.com/2012/01/fuel-control-system.html
Also please refer to the following website
http://aeromodelbasic.blogspot.com/2012/02/proportional-flow-control-system.html


text:
Does the compressor stationary vane have stagger angle?
Does the compressor stationary vane have stagger angle? ( stagger angle is the angle between chord of the blade or vane with engine's longitudinal axis )

The stationary compressors are responsible for guide the air particles flow to the next compressor or stage with an even air flow on the engine's longitudinal axis, taking under consideration angle adjustments in order to avoid air turbulence with may cause a compressor stall.
So, depending of the engine project, the answer is yes. The angle can variate, being static or even with self-adjustment.

Can you provide a source for an engine with self adjusting stator vanes? This is highly dubious. The stator vanes convert the velocity generated by the rotating blades, into pressure, as well as diverting the flow into the next stage of rotating blades. If they were aerodynamically self adjusting, the would not do these two functions as well, wouldn't you agree?

Completely! But there are not aerodynamically adjusted stator vanes. They are just adjusted if the air flow is not even enough in order to avoid a high compressor stall. Unfortunately I don't have any image source open to public. My best regards,

Please take a look at this: https://en.wikipedia.org/wiki/General_Electric_J79

Ok, we are saying the same thing! Regards,

Or, it can be variable. One of the great advances made with the GE J79 was a variable angle stationary vane setup.


text:
What is this very distinct humming noise coming from the IAE-V2500 engines of the A320 during taxi?
So I am a huge fan of the A320, and in a less broader sense, the A320 with IAE-V2500 engines. Arguably the greatest engines in the industry with the greatest sound. However though, I've had a question that I just can't seem to have answered so I'll ask here. If you're sitting inside an A320 with IAE-V2500's and you're taxing out to the runway, you here a very distinct humming noise coming from the engines. What I find confusing about this noise is that it sounds very different on the outside as I have spotted the A320 with V2500's in person, and the idle/taxi sound outside of the aircraft sounds very different from the inside. You can find the sound I'm talking about at timeframe 7:42 until takeoff (taxi) in this provided YouTube video:

Thank you all so much! -Niko

I couldn't hear anything change much at 7:42

I'm not exactly sure what noise you're referring to - do you mean the oscillations in loudness? https://en.m.wikipedia.org/wiki/Beat_(acoustics) (possibly due to N1 and N2 almost syncing up)

@Sanchises, the beat is probably not N1 and N2 almost synching up, it's more likely the left and right engines running at slightly different speeds.  I hear the beat coming in about 6:42 on the video, so maybe OP just made a typo with 7:42?

I don't think there's anything particularly special causing that sound, it's just how the engines sound.
Inside the airplane you're heavily insulated from exterior sounds, so you're not going to hear much of the airflow and fan sounds from the engine.  You're mostly hearing engine sound that travels through the airframe itself, the turbines primarily.
Outside, the engine sound is dominated by the airflow and fan noise.

You may mention that insulation may filter out some sound frequencies and thus distort sounds

I think this is the sound of combustion, as for example it is always the first sound that gets higher in frequency when fuel flow is increased (or engine spools up). Furthermore, the sound is more audible when sitting just above the wing, as this part is quite close to the combustion chamber, so combustion can be heard. It also makes sense as combustion to me should have a sound that is closer to humming than the sound of a mechanical whine such as when the fan spools up.  Additionally, when an engine starts up, it first spools up using the bleed air until a certain rpm where a rumbling sound starts to be produced and gets higher in frequency until it becomes like the hum we are concerned with here. Apparently thats the sound of combustion being introduced.
Not sure though. I’m just trying to make a case here, so don’t take my word.
On a side note, I also like listening to that humming sound, especially when sitting in front of an iae v2500. The cfm56 also has a similar humming sound on both a320 and b737.

mmmmm... edible sound....

i mean audible*  By the way do you have any idea what that humming sound could be? Cause what I wrote is just me guessing.


text:
Is it feasible for an individual with limited current knowledge to undertake the development of an aircraft from scratch?
The world of aircraft engineering is truly remarkable, and even the smallest components involve a wealth of knowledge. I'm eager to explore this field and embark on the journey of building an aircraft. However, I find myself overwhelmed by the sheer volume of available information in books. Could you kindly guide me through the steps and processes I should undertake to start the journey of constructing a small 9-12 seater aircraft? Any recommendations for specific books or resources that could assist me in this endeavor would be greatly appreciated

Anything more than a 2 seater is probably a bit ambitious for a single novice builder

No. Unless it's a model aircraft and you mean 9-12 ant seats.

This is rather broad. There are entire degree programs in college devoted to all the aspects of designing an aircraft, and even then, the graduates enter industry not as "the designer" of something new, but in a more specialized role, continuing to learn for years. Other than as a question for opinions on resource location (i.e. what textbooks do you think are best), I suspect that this question is unanswerably broad.

Are you an engineering with a lot of experience (possibly from an hobby) to make things? If you want just to learn: do a model aircraft. Easier and safer for most purposes (cheap materials and cheap to build a structural solid stuff, and you find stuff to buy). Think just about choosing an engine: could you find manufacturers and get an engine which fit your task? It is too expensive for try and error (but for a small model aircraft). And it is one of the easiest task.

It's not possible to solo-develop a 9-12 seat airplane to a legally flyable condition. The authorities want passenger aircraft built by people who know what they're doing, then checked again by another set of experts. For a 9-seater, the certification paperwork alone will take more time than a single human's lifespan.
Bjorn Ferhm, an aerospace engineer and a test pilot, has done a brief 34-part series of articles on what it takes to develop a small commuter airliner. He speaks from experience, and it's split into easily readable sections.
Part 5 covers the certification rules. A 9-seater will be FAA Part 23, Level 3. Anything more than 9 seats will be Level 4. The rest of the articles covers exactly the kind of airplane you envision. I strongly suggest you read through the whole 34-part adventure - it's what you'll do when designing the aircraft. Navigation is a bit challenging in there, but you can find it all browsing by author.
Here's a simplified to-do list to get a plane like that into the air.

You could skip a few steps for a one-off, but most are still necessary.
These articles won't tell you how to do all these things, only what to do. For how to do it, Daniel Raymer's Aircraft Design: A Conceptual Approach, widely available online, is the perfect start. It will get you to being able to create a brochure with a realistic aircraft proposal.
You'll need at least a dozen more books on aircraft design to finish the plans, and as many to manufacture them. Realistically, the easiest way to get it done is to study aerospace engineering in a good college, working with your fellow students. As a class, you'll often have a chance to design and build a manned aircraft prototype over the course of your 4-year degree. It will usually be a 1- to a 4-seater, but it will be the experience you need to go further.
The good news is: the rules for 1-seat experimental ultralights are very relaxed compared to anything else. You can build almost anything you want, as long as it flies reasonably low, slow, and doesn't carry anyone else. Specialized knowledge/education is still strongly advised in order to succeed with a new design, but it's possible solo.

Re " as long as it flies low, slow" -- In the USA, there's no altitude limit short of 18K MSL for ultralights.   I've had mine up to 16K MSL and AFAIK I was breaking no regs.

@quietflyer True that. Just reasonably low, not into the commercial flight levels.

To quote Douglas Adams: “ Human beings, who are almost unique in having the ability to learn from the experience of others, are also remarkable for their apparent disinclination to do so.”

Hmm. I'm wondering why this question makes me think of @PeterKämpf


text:
What should the inlet to throat area ratio be for a CD rocket nozzle on an aircraft flying at Mach 10?
I am analysing a rocket CD (convergent-divergent) nozzle at a altitude of 15,000m. I am stuck on how to calculate the areas so that at the throat of the nozzle Mach number equals to one. The atmospheric parameters at 15,000m I have taken to be:

temperature=216.7k,
P=12,110pa and
speed of sound to be 295.1m/s.

The weight of the hypersonic plane being 164kg, fuel used is hydrogen so gamma=1.4 and R=4.124KJ/kg.k. For the total temperature at the inlet I have to be 2527.039K and assumed the pressure to be 1000kpa.
I want the aircraft to fly at Mach 10. I am really struggling on how to get the inlet area to throat area ratio.

Is this a rocket or a Ramjet? Drawing and description feels like a ramjet, but you keep saying rocket.

@federico it is a rocket

so what are the combustion chamber conditions M1 P1 T1, etc?


text:
Can weather groups contain multiple descriptors in a METAR?
I understand that a weather group in a METAR is composed of qualifiers (intensity, descriptor) and the weather phenomenon: precipitation, obscuration and other phenomena.
My question is can weather phenomena have multiple descriptors? Eg: Are TSSH or TSSHRA valid in a METAR?

No, a METAR descriptor can only appear once in a METAR or line of a TAF. That is because METARs and TAFs report weather phenomena in the format of
[Intensity][Proximity][Descriptor][Precipitation][Obstructions to Visibility].

Thunderstorms, for example, are one descriptor; therefore, thunderstorms (TS) will only appear once.

Intensity
Applies only to the first type of precipitation reported. A “−” denotes light, no symbol denotes moderate, and a “+” denotes heavy.
Proximity
Applies to and reported only for weather occurring in the vicinity of the airport (between 5 and 10 miles of the point(s) of observation). It is denoted by the letters “VC.” (Intensity and “VC” will not appear together in the weather group.)
Descriptor
These eight descriptors apply to the precipitation or obstructions to visibility:
TS = Thunderstorm
DR = Low drifting
SH = Showers
MI = Shallow
FZ = Freezing
BC = Patches
BL = Blowing
PR = Partial

Precipitation
There are nine types of precipitation in the METAR code
RA = Rain
DZ = Drizzle
SN = Snow
GR = Hail (1/4" or greater)
GS = Small hail
PL = Ice pellets
SG = Snow grains
IC = Ice crystals
UP = Unknown precipitation

Obstructions to Visibility
There are eight types of obscuration phenomena in the METAR code
FG = Fog
HZ = Haze
FU = Smoke
PY = Spray
BR = Mist
SA = Sand
DU = Dust
VA = Volcanic ash

A + or - can be added to indicate intensity. The OP is asking about other alpha symbol intensities such as their example of THunderstorms with SHowery RAin or THunder SHowers. So far, I have not found any further citations for neither TSSH nor TSSHRA. Have you seen any such METAR reports?

I've not seen TSSH in any METAR that I can recall. I often see +TSRAGR BR.

@DeanF. Please see my edited posted for clarification. TSSH and TSSHRA cannot appear in the same METAR.

Your question brought to my mind the following question. Since TS and SH are both descriptors that indicate the intensity of precipitation, can they both exist simultaneously? Sort of like when does fast become slow? Or, in the case of the weather phenomenon RA, at what point does gray become black or white instead of both? A quick google search turned up the following article from a local meteorologist.
Thunderstorm, Thundershower...What's the Difference?
March 16, 2001 at 1:51 AM EST - Updated July 1 at 10:45 AM
What's the difference between a
thundershower and a thunderstorm?  That is
a question that has a technical and
psychological answer.  Technically, any
cloud producing lightning is considered a
thunderstorm, even if there is no rain
falling.  The National Weather Service
reports it as "TS" in their hourly
observations at the airport.  TSRA means a
Thunderstorm with a Rain Shower, which is
what most of us think of when we think of
thunderstorms...Thunder, Lightning and
Rain.  But, when meteorologists (Mainly on
TV and Radio) want to indicate that
thunderstorms with light rain are expected,
they will call them Thundershowers, even
though there is no technical abbreviation
for a thundershower.  It's just a good way
of taking the much stronger sounding word
"storm" out of the mix, and adding the
gentler sounding description of "shower".
Properly, thunderstorms have either no rain
(TS), light rain (TSRA-), moderate rain
(TSRA), or heavy rain (TSRA+).  But, for a
viewer, it's tough to explain all that, so
we generally talk about weaker
thunderstorms as thundershowers, even
though there is "technically" no such
thing.

With this type of argument, TS and SH remain completely separate (eg. TSRA vs. SHRA). The + or - would be added to indicate intensity.


text:
Why should one not slip a Cessna 172 with flaps extended?
The POH strongly recommends not slipping the AC with full flaps...why?
It seems natural in a crosswind approach to
allow the horizontal lift component to cancel the airmass movement across the centerline.

Fastest edit ever!  I predict a massive response from our two resident sideslip experts, complete with breakdown of all forces, real and imaginary.  Plus the effect on the ball.  (I wont name either of them...  ;)

I'm pretty sure this has been answered on ASE.  I seem to recall the answer has to do with the turbulent wake on the horizontal tail and a resulting loss of pitch stability.  Not sure why this would be different in a slip than in non-slipping flight though.  Have experienced a weirdness in pitch control when slipping with full flaps though, esp in the versions where flaps went to 40 degrees.  Can't recall whether said weirdness was a nose-drop tendency, or just a marked reduction in yoke pressure per unit change in elevator position away from trim, or what exactly.

@Bianfable -- Thanks for the edit, seeing as a Cessna 172 is not a military cargo aircraft.

The use of full flaps can blank the airflow going over the tail, resulting in loss of pitch control; not good when at low altitude coming in for a landing.

@CrossRoads -- that could be an answer.  Yes I seem to recall that in the situation referenced in my comment, larger-than-normal movements of the yoke were needed to control the aircraft's pitch attitude.

Perhaps the question has not been actually asked before on ASE.  Here is an answer that sheds some light on it though-- see associated comments -- https://aviation.stackexchange.com/questions/39314/is-there-any-disadvantage-to-slipping-as-a-way-to-lose-altitude/39317#39317

Not to be picky, isn't it greater than 20 degrees of flap, not full flap? Some models of 172 have 2 more settings past 20, and I'm pretty sure the direction is no sideslips past 20 degrees

The basic problem is that sideslip induces a cross flow over the fuselage that can increase the local negative AOA and flow disruptions beyond that already caused by the turbulence and downwash being generated by the flaps.  The stabilizer surface on the "lee" side of this cross flow may get enough flow disruption to be felt in the elevator, maybe accompanied by a bit of pitch bobbing at some extreme condition that maximizes the tail loading, like side slipping at forward C of G with large flap angles.  In spite of its very powerful flaps, the 172's issue is fairly benign (or there would be a prohibition against using slips with flap as opposed to an advisory).

This can be a significantly worse problem with stabilator or all-flying tails that operate at larger negative AOAs than fixed stabilizer tails, as Cessna Cardinal owners are well familiar with.  The Cardinal required slots to be added to the stabilator inboard leading edge to fend off tail root stall during landings, and resulting broken nose gears, during the first year of production, and that was just doing regular landings with maybe a bit of slip due to crosswind (the '68 Cardinal I once owned had the field mod slots added under the "Cardinal Rule" service bulletin - Cessna sent teams out to modify every aircraft pre production cut-in in 1968, somewhere around 500 a/c, and you can slip them with flap all you want).
The stabilator equipped Thorp T-18 homebuilt had to have a flap limitation added due to stabilator stall in sideslip (John Thorp did some testing after an incident in the 60s, discovering that the stabilator could stall with full flap, forward CG and sideslip, causing a nasty pitch over, and advised owners not to use full flap for landing).

That is a very good drawing of an empennage!

There could be several reasons for such recommendation, but specifically for C172, its POH explains it as follows (section 'Normal Landing'):

Steep slips with flap settings greater than 20° can cause a slight tendency for
  the elevator to oscillate under certain combinations of airspeed,
  sideslip angle, and center of gravity loadings.


text:
Does endurance include the fuel reserve time?
I have been wondering if endurance time actually includes the fuel reserve time?
For example:

Total usable FOB = 84 litres
Fuel burn rate = 16 litres/hour
Aircraft's reserve fuel = 30 minutes

Therefore is the endurance time 5h 15mins, or 4h 45mins?

Are you referencing the POH to get endurance time or a company document or flight plan?  Surely the POH would not list endurance with a fuel reserve.  Flight plans and company documents may adjust the POH numbers to provide such reserves.

Endurance is the length of time the aircraft will fly for a given set of conditions. There is no reserve fuel built into aircraft or their designs, because there's  no constant definition of reserve.
The reserve is defined by the pilot/captain/law depending on the circumstances, and is simply defined as the extra fuel/endurance required in addition to the expected mission requirement.
The answer to your question is that, based on your fuel burn you have 5hr 15minutes endurance. If you need 30 minutes reserve, then the longest you can plan to fly is 4hr 45 minutes

Endurance time probably does include  reserve time, though this is not made a specific stipulation as per ICAO Annex 2, Annex 6 nor in Doc 9976 (Flight Planning and Fuel Management).
Based on the nature of your question, where you give an example, I presume you are concerned about flight planning.

A flight plan shall comprise information regarding such of the following items as are considered relevant by the appropriate
ATS authority: ... ... - Fuel Endurance
ICAO Annex 2 Rules of the Air - 3.3.2 Contents of a flight plan

Sections 4.16-4.26 of ICAO Doc 9976 outline pre flight planning for fuel but does not define fuel endurance. Neither does Annex 2 and 6.
None the less, the best interpretation of all of this is that it would make sense that endurance does include reserves, it lets ATS know when the aircraft will continue to fly with its engines running. Also 'complete' fuel endurance (including reserves) is good for emergency dead reckoning crash site location estimations.
So let the ATS know via flight plan or booking out that your endurance fuel is 5hr 15 mins


text:
What are the differences between direct law and mechanical back-up?
I am learning for an avionics exam and I cannot find any differences between the direct law and the mechanical backup.
I will describe the laws that I learned such that it is easier to see if I have some misconceptions.

Normal law: Standard mode of operation
Alternate law: (at least two failures detected):

Loss of pitch and bank protection
$\alpha$-protection and high-speed protection replaced by stabilities
Load factor limitation is still active

Direct law: (at least two failures second not self-detected)

All protections lost
Manual pitch trim

Mechanical back-up: (all electric supply for control computers lost)

All protections lost
Manual pitch trim

Is the only difference between the direct law and the mechanical
back-up that we do not have operating computers for control?

feed back loop.

Yes. Mechanical backup on Airbus encompasses the mechanical links between trim/elevators and pedals/rudder. Laws are related to the joystick and flight control computers. See this answer which should provide all the elements to answer the question.

The last line should be “Manual pitch trim only”, because only the trim wheels and rudder pedals have hydromechanical linkage.

The key piece of knowledge to understand a FBW system is that you need to differentiate between signalling and actuation.
signalling is what tells the control surface to move and to what position. In old airplanes, this was by steel wires. In FBW airplanes it's by copper wires carrying an electrical signal.
actuation is what actually moves the controls surfaces to the commanded position, the muscles. Traditionally this is hydraulics, but you can also find electric actuators these days.
For the Airbus, Normal, Alternate & Direct all use electrical signalling (whether produced by computers or not). But what to do if there's no electrics? That's Mechanical backup, where you have steel-wire signalling of specific surfaces.

Does Airbus have mech backup?

@Caterpillaraoz - see this question and others like it here.

@Caterpillaraoz, the A320 does as does A330 and A340, but I had the impression that A380 does not.

Well, the important bit is that the side-stick is only connected to electric sensors, so in the mechanical backup mode it does nothing and only the trim wheels and rudder pedals work.


text:
What is the origin of the term "military power"?
An engine producing 'dry' thrust is said to be at 'military power', a useful distinction from reheat / afterburner.
It's always seemed an odd phrase to me. There's nothing particularly military about it, and why would afterburner not be military? 'Military' has always been used as a word that always relates to soldiering in some form or another - it is a curious choice to define the operation of a jet engine.
It must, of course, be a twentieth-century phrase. Can any light be thrown on its origin?

The etiology of military power is from War Emergency Power (WEP) which in the WWII era was a higher than normal rating power (i.e. >100% rated power) setting on an aircraft engine.  Such power settings were approved for short durations (typically 5 minutes or less) such as takeoff and battle maneuvers.
The term was quickly shortened to military power.
Sometimes military power is assumed to be simply full throttle, but that may not be accurate, particularly in blown engines, where turbochargers or superchargers may be set to permit higher than normal air delivery to the combustion chamber.
Finally, military power was used for more extended periods of times, when conditions dictated, but at a reduction in reliability and service life.  Sometimes in war, service life is not a pilot's greatest concern.

Thanks, I think the confusion is because (notwithstanding your answer) "full military power" - a fairly common phrase - is really an oxymoron. It can give the impression that "military power" is "normal power", when it's really not. Makes its etiology much clearer.

Interesting you used the word etiology, @PartyArk. One contributor suggested a different word, etymology, which is the study of words. The definition of etiology which I rely on is: the investigation or attribution of the cause or reason for something, often expressed in terms of historical or mythical explanation. Some people think etiology is disease oriented, but the term is frequently used in other engineering or scientific contexts.  The military power explanation I gave is essentially what was shared with me by Dick, who was the FE on the B-17 "Fuddy Duddy" in WW II.

"Military power" is less about the distinction between dry and wet thrust, but more about the distinction between civilian "maximum power" and "military maximum powerÄ which usually puts more strain on the engine than desired in a civilian context.


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What is the practical usefulness of a small home made wind tunnel?
Is a small wind tunnel, like in the video, of any value for building planes able to carry a man?
Can the lift and drag, corresponding to a scaled down wing (or segment of a wing) introduced in such a tunnel, be scaled up to obtain the lift and drag of the full size wing?

See this video

Note that this wind tunnel in particular is a poor example, because the test specimen is the same size as the tunnel, while it should be an order of magnitude smaller.

@Sanchises If you have an example of another home made wind tunnel better suited for designing large wings that can not be tested inside it, please post here a link to it.

One of our EAA members is on the faculty at Cal Poly and arranged a tour of their wind tunnel. It wouldn’t fit in your garage, but it’s not too much larger. The students use it for all kinds of aerodynamic research. The chamber is about 3 feet square and maybe 12 feet long. https://aero.calpoly.edu/facilities/windtunnel/

@JScarry , Should I understand, from your recommendation regarding that wind tunnel used at Cal Poly, that the small wind tunnel used by the Wright brothers (see:http://www.solarnavigator.net/inventors/wright_brothers_wind_tunnel.htm) was useless for designing their gliders and planes? I mean the two inventors could not have scaled up the lift and drag measured on scaled down segments of wings, with the help of their tunnel.

@RobertWerner No.

Is a small wind tunnel, like in the video, of any value for building planes able to carry a man?

The short answer is NO!
To be more clear if, as an example, one has a small wing and measures its drag coefficient, with the help of a small wind tunnel, this coefficient is simply useless for a wing of the same shape but with a surface: 25, 50, 100 times larger.
"Scaling from the tunnel to the Wright Flyer ... showed the Wrights’ drag prediction to be 300% too high, resulting in highly inaccurate efficiency predictions. ... the Wrights’ quantitative data was not applicable to full scale design." (From the study of Michael Gary Dodson)
The Wright Brothers just wasted their time with the wind tunnel they had built. They could not have used the numerical data obtained from such experiments for designing large wings.
The two inventors from Dayton just copied the Voisin - Farman - Delagrange wings, which they saw in 1907 when they spent about 6 months in Europe, and then built a plane in 1908, powered by a French engine, Bariquand et Marre, and flew for the first time near the town of Le Mans, on August 8, 1908.
For more information you can read this new free book:
A. I. Root, the liar number four after the Wright Brothers and their mentor, Octave Chanute

The main two witnesses of the Wrights, Amos Ives Root, from Medina, Ohio and Octave Chanute from Chicago did not see the two inventors flying on September 20, 1904, and October 15, 1904, respectively, as they claimed.
The December 17, 1904, "successful" trials performed near Kitty Hawk (an isolated place far from civilization) represent nothing in comparison with the 105 flights at Huffman Prairies (near Dayton), claimed by the two brothers for the year 1904. No credible witness saw them flying that year.

"The short answer is NO!" I wonder why then wind tunnel tests are done at all (hint: because with the right analysis the short answer is YES)

There are some things about this wind tunnel that are not as good as the best wind tunnel experiments for actual aircraft.
Obvious concerns are that the wing is very close to the bottom of the wind tunnel (relative to the size of the wing), which means there will be a kind of "ground effect."
(Notice how at the high level of attack shown in your photo, the airflow underneath the wing is almost completely pinched off.)
The relative nearness of the top of the tunnel could have an effect too.
The setup shown will not tell much about what happens at the wingtips of an aircraft--an airplane with huge vertical plates attached to the end of each wing (which is what this setup models, with its wing tip practically flush to the side wall of the tunnel) will fly differently than an otherwise identical aircraft without those vertical plates.
Merely testing the wing also doesn't tell us anything about the aerodynamics of the fuselage, which will affect how well the aircraft flies.
There are also scaling issues having to do with things such as
Reynolds numbers and (for jet aircraft) Mach numbers.
Practically all wind tunnels have these kinds of scaling issues.
The "aircraft" that are tested in them are generally scaled-down models.
This is something that wind-tunnel experts have learned to deal with
(see Peter Schilling's answer).
But while those are things of concern to people building the latest passenger jets and fighter aircraft, where flying just a little better than the competition is very valuable, I think a wind tunnel experiment like this is meant to investigate more basic properties of wings.
When the Wright Brothers were building their first aircraft, for example, the aerodynamics of wings was not very well understood at all.
Even a few years ago, incorrect notions about wings were widespread
(there are whole pages of the NASA website debunking them).
If a wind tunnel like this gives you information about the forces on the wings that is 30 percent more or less than the "true" values,
you're still way ahead of someone who is basically just guessing about the forces by combining naïve intuitions about the dynamics of the airstream with calculations based on actual speed, density, and so forth.
My biggest complaint about the design of this apparatus is that the arrow attached to the wing, pointing to the angle scale on the back wall, cannot measure negative angles of attack. This could be fixed by mounting the angle scale with the straight edge of the scale vertical instead of horizontal.

The Wright brothers certainly thought so, and with obvious results. I highly, highly recommend McCullough's book if you'd like to learn more:

Though such apparatus did not look like much, it was to prove of immense value. For nearly two months the brothers tested some thirty-eight wing surfaces, setting the “balances” or “airfoils”—the different-shaped hacksaw blades—at angles from 0 to 45 degrees in winds up to 27 miles per hour. It was a slow, tedious process, but as Orville wrote, “those metal models told us how to build.”

For a more contemporary look at scaling methods, see this paper (there are many others, too).

Second on the McCullough book... Great read!


text:
Is there an indication in the cockpit when the refueling control panel door is open on the ATR72?
Is there any indication (light, MFD/SD displays) in the cockpit of opened/closed refueling control panel door in ATR72-600?

From these notes valid for ATR42 and 72: "No warning if a fuel door, ground air conditioning access door, emergency exit, etc. is open.  Must check refueling panel door before flight if it was not closed during preflight or if it was opened after the preflight was completed."


text:
How can the Cirrus Vision jet be cheaper than its competition?
Cirrus Vision SF50 costs USD 2 million, compared to USD 5 million for comparable private jets.

How is Cirrus able to offer a jet at such a substantially lower price? What compromises are customers making when buying this plane versus a competing one (Eclipse Canada, Cessna Citation M2 and Embraer Phenom 100 as per https://www.usatoday.com/story/money/2017/07/06/price-cutting-private-jet-shakes-up-aircraft-market/102607220/).

I'm not sure those are competing. The Vision is significantly smaller and single engine. I'm not even sure the Phenom is single pilot. (Edit: it is)

Most of the "comparable jets" are at least 10,000 lb MTOW. The SF50 is much smaller, at 6,000 lb MTOW. Half the size, half the price, roughly. The Eclipse 550/Canada would be a better comparison, it's a similar weight but it flies faster and further.

Why does the video say "But Girl Scout membership has been declining since 2008" at 0:45?  Was the video hacked?

I read an article on the SF-50 recently published in AOPA Pilot and, to be honest the Cirrus Jet is not even in the same league as the other aircraft mentioned.  People think 'oh it's a jet for $2 mil - I want one' but remain fairly ignorant of exactly what that means compared with other jet aircraft.
The primary differences in performance between the Cirrus and other light jet aircraft is that it's much slower and suffers from 'short legs'.  Depending on payload, the Vision has about at 600 NM range at its max cruising speed of 300 KTAS, burning a stiff 84 gallons/hr.  It sounds enticing to an SR-22T owner looking to upgrade, but consider that high end turboprops like the TBM-9XX are leaving you in the dust by at least 20 knots and using 40% less fuel to do so.  Ranges of approx 1200 NM are possible, depending on payload, but at an economy cruise of 240 KTAS, making it faster than the owner's old SR-22T but slower that nearly all turbobprops and probably more expensive to operate.  The Vision is also not RVSM certified, limiting operations to 28,000 ft.  As a yardstick for comparison, an Embraeer Phenom 100 with a similar sized cabin, at roughly twice the cost of a Vision is capable of over 400 KTAS (Mach 0.70) at FL410 with an 1100 NM range with alternate and IFR fuel reserves.
Ther are other items that aren't immediately visible but play an important factor in the cost difference, chiefly cabin environment.  The Vision's pressurization isn't on par with similar jets, probably being limited to a 5-6 psi cabin differential, yielding around an 8,000 ft cabin altitude at 28000 ft.  The Cirrus is spacious compared with an SR-22 but it's nothing impressive when it comes to light jets and it's not even in the same league as larger jets.  Many of the systems do not have the creature comforts of the big boys e.g. The Cirrus still uses a castering nosewheel as opposed to NWS equippped on most jets, etc.
The Cirrus represents a solid, if somewhat expensive, upgrade from the SR-2X aircraft.  Just don't expect it to be a personal 747; it's not and you do get what you pay for.

Why would they choose not to certify it for rvsm? Is the single engine not capable of going much higher than FL280 anyway?

Most of its competition has 2 jet engines. Jet engines are very expensive. The Vision only has one engine!

The cost of the engine is estimated at around $44,000, I doubt that the "bells and whistles" add up to $954,000+... Just like the SR-22 at $650k+ doesn't have a $325,000 engine, I doubt that the cost of the SF50 is 50% allocated to the engine itself...

If that is true that blows my mind. When I worked for a small regional airline years ago, the PW engines on the small jets were $5M+ each. But that price point is estimated assuming economies of scale, but even so, that is amazing.

@RonBeyer its just hard to believe that it can be that cheap. The overhaul price for a cessna caravan turbo prop is close to $250,000. I find it hard to believe that a modern turbofan jet new, can cost less than the overhaul price of a cessna caravan overhaul.

@RonBeyer that article was published in 2008, and is coming from a guy who was not talking about existing engines: Merrill's engine for the Cloudster [has] a specific fuel consumption of around 0.30 pound per hour per pound of thrust—an extraordinarily low number, [...] 50 percent better than the current VLJ mainstay engines. [...] Merrill estimates the cost of a production engine at $44,000. Might be worth finding a newer source.

There is no way Cirrus is going to bet the farm on a $44K unproven hypothetical engine. They instead chose the FJ44 engine by Willimans which power everything from the Cessna CJ (entire line), Premier, PC-24 and more. It's easy to say you can make it cheaper, but no one has yet!

The SF50 was designed to meet a gap in performance between high end turbo props and the 4 to 5 $M Jet.
So its not supposed to be as fast, or as high, or fly as far as the Phenom 100.
The comparison to the TBM seems a little biased.  We highlight a range scenario where the SF50 is heavy and at max fuel burn and then attempt to compare it to an aircraft with a lighter load lower power setting with the statement "depending on payload, but an economy cruise...".
If we were to compare apples to apples and go max power and max gross on both aircraft, im sure that economy cruise would go right out of the window.  Thus putting the SF50 squarely where Cirrus intended it to be in the first place.  Not as fast or high as the more expensive options, but not as slow and low as some others.
As for the difference in cost, there are several factors that come along with production of not just another engine, but the nacelle and material to structurally mount the thing, design and engineering labor to make that work, additional labor cost t mount it, test it and any maintenance or warrant programs that may be associated with it, flight testing single engine aerodynamics and flight characteristics, certification, and lets not forget the obligatory profit that has to be attached as well.  After all, no one makes airplanes for charity do they?
As has been stated already, Does that make up for the total difference in cost?  Most likely not.  But my response is just a shadow of the reasons why other jets would carry a higher cost.


text:
PA28 Archer 2 Circa 1986 - Noisy Engine
100 hours ago, a group-owned PA28 Archer II Circa 1986, 180hp plane had its engine rebuilt after 2500 hours.  There had been no problems with the aircraft during the 2500 hours.
Since the rebuild, the plane is extremely noisy between 2,200 and 2,350rpm with significant vibration.
The propeller, the timing and the compression have been checked.  Does anyone have any ideas why the plane should suddenly be so noisy in the cruise range?
The noise is a low-frequency booming.

Not enough information. Clattering?  Howling?  White noise? Frequency of the vibration?

Thank you John K - I have edited my question to include this information.

Did they change the muffler at all with the engine? Boomy noises at high RPM is usually more to do with the muffler than the engine itself. Almost impossible to diagnose from a description, what does a qualified mechanic say during a demo ride?

Engine mounts? Loose, overtightened, wrong type (if changed) may generate all kinds of weird resonances. And along the lines of @Jamiec the exhaust system mounts (if applicable) should also be checked.

The propeller beat frequency and the exhaust pulse frequency of a 4 cylinder engine are both about 60-80 hz. At 2300 RPM, 76.6 Hz to be precise.
A booming noise is likely noise in that frequency range (as if it was just the propeller noise amplified).
So two routes of investigation I would follow are propeller and exhaust system.
I would try two things:

Remove the prop and move it one bolt on the hub. You want the blade to be ideally around 10 o'clock with a cylinder near TDC, but there is some leeway to change position. It could just be a coupling of the prop beat and the exhaust pulse beat in some sort of resonant phase that is entered at that RPM range. Reclocking the prop one bolt would disrupt that.

I'd inspect the exhaust and muffler for looseness, contact with structure or engine mounts etc. If the muffler can be shifted slightly in its  brackets, maybe move it a bit.

Try it out after each change, so you know which thing made an improvement if you get results.

A belated and grateful thank you to those who answered my question. Very much appreciated. John B

@JohnB did you get to the bottom of it. As another PA-28 driver it's always good to know


text:
When bailing out of a T6 what is the intended path that the pilot clears the horizontal stabilizer?
My wife and I who have both flown in vintage T-6's in the rear seat have been given instructions to stand on the seat and "dive toward the wing" in the event we need to bail out of the aircraft.
We've haven't been able to agree how a pilot is expected to exit the aircraft and clear the horizontal and vertical stabilizers.
If a pilot bails out of a T-6 is their path supposed to clear the horizontal stabilizer laterally or to pass underneath the horizontal stabilizer as the aircraft passes over?
We've done some basic math and guesstimates but still can't come to a consensus. Can someone with theoretical or real experience in bailouts with non-ejection aircraft help to clarify this?

Good question (and thanks for the edit) -- welcome to Aviation.SE!

I was jumping many years ago. You will travel almost at the T6's speed momentarily as you fall, so if it's flying level at 1G when you go over the side, you drop straight away behind the wing trailing edge without much risk of hitting the tail.
Watch any skydive exit video and observe how fast the jumpers go straight down relative to the airplane.
It gets riskier if the Gs are less than 1, say if the airplane is climbing and arcing over as you exit. When I was skydiving in the 70s, a friend foolishly tried an experiment, exiting the jump plane while the pilot pushed over, hoping to float alongside momentarily.
Instead, being in a near ballistic arc, the drag just took him straight back alongside the airplane and the horizontal tail just contacted the top of his helmet, giving him some stars in his vision, and putting a small dent in the LE of the tail. He never tried that again.

That reminds me of my first time disembarking an aircraft in flight; I had a mental picture of floating away into the distance but in fact I dropped like a brick.  I’ve understood that we’re told ’aim for the trailing edge’ on the understanding that we won’t actually do it but will aim just behind.

That makes a whole lot of sense for straight and level flight! I'm not sure why I didn't think of skydiving when thinking about this problem.
As you mention, however if the aircraft was uncontrollable and diving (which would probably be when you'd be jumping in an emergency) that complicates things and might be too open ended a question.
I suppose as long as you get out even if you get whacked it's better than riding an uncontrollable aircraft to the ground. And maybe that's the answer "it depends, but it's better than staying in".
Thanks!

@tsjackson ... And always remember, any landing you can walk away from is a great one.

@Sharpenologist Wasn't that the definition of a good landing? I thought a great landing is one after which the aircraft can be used again.

@TooTea ... I stand corrected!

@John-K Thanks again, I was able to confirm with an airshow and reno air race pilot who we know that flies a T-6 that this is the intention when bailing out


text:
How to calculate W/V from true HDG/TRK/GS using a CRP-5 flight computer?
I am currently studying for my EASA ATPL (airline transport pilot license) and one of my subjects is General Navigation.
I have stumbled across this question (picture) that has completely stumped me, I have not been able to find help anywhere else. I know it can be solved by drawing wind triangles but I am solely interested in solving it using the CRP-5 flight computer.
I am very much used to calculating desired headings for a certain track when given wind, but not the other way around. Any help would be greatly appreciated.

Answered here:

@mins thanks for the solution, I was looking more for an explanation as to WHY it is done that way so that I can be prepared for any variation, although your response did help me a lot!

Hi and welcome to Aviation SE. If that's the intent of your question, then please edit it to make it clearer. At it's simplest, you are just solving a triangle of velocities. Given two, find the other one.

CMC's answer seems quite complete, with explanations. Explain in your question which part you feel is not logical.

To work this problem in reverse:

Set the True Course (Track) at the Index and slide the grommet over the Ground Speed (GS) of 242 knots:

Draw a dot with an arrow behind it, marking the wind vector at the intersection of:
a)  8° right of center because the wind correction angle or heading is right of course (74° TH minus 66° TC); and
b)  230 True Airspeed (TAS)

Now, above, you are able to visualize the flight.  You could even draw your airplane in the middle and see the wind is a right quartering tailwind.

Finally, rotate the wind to the Index to read the answer.  Slide the center grommet over any line that's easy to read.  Read the wind speed up from the grommet (35 knots) and wind direction (from 180°) at the index:

Ironic: after well over  a decade of airline flying (this being a question for an ATP test), I'd be in desperate need of a refresher course on these tools in order to be able to solve this problem.  Heck, I don't think I ever did anything like this in the Air Force after leaving pilot training.  I'll grant that it's good to know the theory behind what the FMS and flight planning software is doing, but as far as a practical skill to have, this stuff isn't on the list. Not even close.